Blocking Hsp70 Enhances the Efficiency of Amphotericin B Treatment against Resistant Aspergillus terreus Strains

Abstract

ABSTRACTThe polyene antifungal amphotericin B (AmB) is widely used to treat life-threatening fungal infections. Even though AmB resistance is exceptionally rare in fungi, mostAspergillus terreusisolates exhibit an intrinsic resistance against the drugin vivoandin vitro. Heat shock proteins perform a fundamental protective role against a multitude of stress responses, thereby maintaining protein homeostasis in the organism. In this study, we elucidated the role of heat shock protein 70 (Hsp70) family members and compared resistant and susceptibleA. terreusclinical isolates. The upregulation of cytoplasmic Hsp70 members at the transcriptional as well as translational levels was significantly higher with AmB treatment than without AmB treatment, particularly in resistantA. terreusisolates, thereby indicating a role of Hsp70 proteins in the AmB response. We found that Hsp70 inhibitors considerably increased the susceptibility of resistantA. terreusisolates to AmB but exerted little impact on susceptible isolates. Also, inin vivoexperiments, using theGalleria mellonellainfection model, cotreatment of resistantA. terreusstrains with AmB and the Hsp70 inhibitor pifithrin-μ resulted in significantly improved survival compared with that achieved with AmB alone. Our results point to an important mechanism of regulation of AmB resistance by Hsp70 family members inA. terreusand suggest novel drug targets for the treatment of infections caused by resistant fungal isolates.